Electric incandescent lamp and method of manufacturing same

ABSTRACT

The invention relates to an electric incandescent lamp which comprises a lamp cap having hollow contact pins, in which current conductors emerging from the lamp envelope are soldered in the cavity of the contact pins. On the free end of the contact pin the cavity is open and shows a narrowing in which the current conductor projects with a small amount of play. The part of the cavity present near the free end of the contact pin and a part of the narrowing are filled with soldering material. The invention furthermore relates to a method of manufacturing such an incandescent lamp in which during the soldering operation the contact pins assume a position in which their free end is uppermost. The invention finally relates to an incandescent lamp manufactured by said method.

Unite tates Patent [191 De Fraeye et al.

[4 1 Feb. 25, 1975 1 ELECTRIC INCANDESCENT LAMP AND METHOD OFMANUFACTURING SAME [75] Inventors: Dirk Jules Remi De Fraeye; Jan

Alfons Catharina Mewissen, both of Emmasingel, Eindhoven, Netherlands[73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Aug. 20, 1973 211 Appl. N04 390,166

[30] Foreign Application Priority Data Sept. 13, 1972 Netherlands7212382 [52] US. Cl 313/318, 313/222, 339/144, 339/275 B [51] Int. Cl1101] 5/48, I-IOlj 5/50 [58] Field of Search 313/222, 318,113,; 339/244,245, 246, 144, 145, 146, 275 B,

[56] References Cited UNITED STATES PATENTS 2,745,982 5/1956 Breadner etal. 313/318 X Primary ExaminerAlfred E. Smith mhmatfiaeemiaes fieChatmom Attorney, Agent, or Firm-Frank: Trifari [57] ABSTRACT Theinvention relates to an electric incandescent lamp which comprises alamp cap having hollow contact pins, in which current conductorsemerging from the lamp envelope are soldered in the cavity of thecontact pins. On the free end of the contact pin the cavity is open andshows a narrowing in which the current conductor projects with a smallamount of play. The part of the cavity present near the free end of thecontact pin and a part of the narrowing are filled with solderingmaterial. The invention furthermore relates to a method of manufacturingsuch an incandescent lamp in which during the soldering operation thecontact pins assume a position in which their free end is uppermost. Theinvention finally relates to an incandescent lamp manufactured by saidmethod.

4 Claims, 4 Drawing Figures ELECTRIC INCANDESCENT LAMP AND METHOD OFMANUFACTURING SAME The invention relates to an electric incandescentlamp which comprises a lamp cap of an insulating material which hashollow contact pins, in which a current conductor emerging from the lampenvelope is soldered in the cavity of each pin. Such an electricincandescent lamp is known.

In manufacturing said known incandescent lamps which are usuallyconstructed as projection lamps, the soldering operation consists inthat a member of a solid soldering material which is inserted into thecavity of the pin together with the current conductor is melted byheating after which the current conductor is secured in the contact pinupon cooling and solidification. The member of solid soldering materialis inserted into the cavity of the pin via an aperture in the pin, saidaperture being present at the area where the pin is secured to theinsulating material of the lamp cap. As long as the soldering materialhas not yet solidified, the lamp envelope can be aligned relative to thelamp cap for example, by optical means. After termination of thesoldering operation, the lamp cap is filled with cement to reinforce theconnection of the lamp envelope to the lamp cap.

The drawback of this known method of manufacturing is that upon heatingthe soldering material in the pins, which heating may be ahigh-frequency heating and also a heating by means of gas flames, thematerial of the lamp cap is also heated in the proximity of theconnection of the contact pins. This results in a nonuniform expansionof the material of the light cap, which, in particular with thefrequently used ceramic material, may give rise to cracking of the lampcap.

It is the object of the invention to provide an incandescent lamp thecontact pins of which are constructed so that during the manufacture ofsaid incandescent lamp the possibility of damage to the lamp cap is verysmall.

For that purpose, the electric incandescent lamp of the above-mentionedtype according to the invention is characterized in that a space whichopens into the free end of the contact pin remote from the lamp capforms part of the cavity, said space being at least partly filled withsoldering material and, viewed in the direction of the lamp cap, havinga narrowing through which the current conductor projects with a smallamount of play. This design of the contact pins makes it possible thatduring the soldering operation a member of a solid soldering material isintroduced into the aperture of the said space. This member may evenproject beyond the contact pin: in this case the contact pin should bekept with its free end uppermost during melting of the soldering memberso that the liquid solder flows into the aperture of the contact pin.Because in this case only the part of the contact pin which is farthestremote from the lamp cap is heated, the possibility of damage to thelamp cap is very small.

When the soldering operation is carried out with the free end of thecontact pin uppermost, the possibility exists that the liquid solderlands in the lamp cap via the play between the inner wall of thenarrowing and the current conductor, which is undesirable because thewarm solder gives rise to a local rise in temperature. In order toprevent this, the amount of the play, the viscosity of the solder, thetemperature of the contact pin and the length of the narrowing should bechosen to be so that the limit of the solidified mass of solder presenton the side of the lamp cap lies within the narrowing.

The narrowing, viewed from the free end of the 5 contact pin, preferablyhas a portion which widens in the form of a funnel. This actuallyfacilitates the insertion of the current conductor into the contact pin.

The invention furthermore relates to a method of manufacturing one ofthe above-described electric incandescent lamps in which a member of asolid soldering material inserted into the cavity of a contact pintogether with a current conductor is melted by heating and uponsolidification secures the current conductor in the contact pin, whichmethod is characterized according to the invention in that the solderingmaterial is inserted into the cavity of the pin via the aperture in thefree end of the contact pin remote from the lamp cap, the contact pinduring the soldering operation assuming a position in which saidaperture is uppermost. As already stated above, the advantage of thismethod is that damage to the lamp cap does not occur. Actually, in thisposition of the lamp cap the material thereof is not heated by risingwarm air, while it is possible to arrange the heating members in suchmanner that mainly the free end of the contact pin farthest remote fromthe lamp cap is heated.

A favourable embodiment of the method according to the invention ischaracterized in that the member of solid soldering material after itsprovision into the aperture of the contact pin and prior to melting saidmember projects partly outside the contact pin. Upon heating, liquidsoldering material flows into the aperture of the contact pin. Anadvantage of this embodiment is that the heating of the solderingmaterial occurs directly; in the known method on the contrary theheating of the solid member of soldering material is carried out by theheating of the contact pin.

A further favourable embodiment of the method according to the inventionis characterized in that the member of solid soldering material ishigh-frequency heated while using a coil which surrounds the part of themember projecting beyond the contact pin and the free end of the contactpin. With this arrangement of the high-frequency coil, heating of thematerial of the lamp cap is substantially entirely prevented so that thepossibility of damage to the lamp cap remains very small.

According to still another favourable embodiment of the method accordingto the invention the member of solid soldering material has the shape ofa helically wound wire. This member of solid soldering material,however, may also be shaped as a hollow cylinder which is manufactured,for example, of bent sheet material.

The invention furthermore relates to an electric incandescent lampmanufactured by any of the abovedescribed methods.

The invention will be described in greater detail with reference to thedrawing, in which:

FIG. 1 is a longitudinal sectional view of a contact pin during themanufacture of an electric incandescent lamp according to the invention,with the member of solid soldering material used,

FIG. 2 shows the contact pin shown in FIG. 1 after the solderingoperation,

FIG. 3 shows diagrammatically a device for connecting the lamp cap tothe lamp envelope by the method according to the invention, and

FIG. 4 shows another embodiment of the member of solid solderingmaterial.

The contact pin shown in FIG. 1 comprises a cavity which is mainlyconstructed from three parts: the upper space 2 which opens into theatmosphere, the narrowing 3 which changes into a widening 4. A currentconductor 5 is inserted into the contact pin 1, while a helically woundmember 6 of soldering material is arranged above the contact pin andpartly in the space 2. The transition from the widening 4 to thenarrowing 3 is in the form of a funnel so that when inserting thecurrent conductor into the contact pin it easily finds its way in thecavity of the pin. Only a very small amount of play exists between thecurrent conductor and the narrowing 3. FIG. 1 furthermore showsdiagrammatically a high-frequency coil 7. By heating the member 6 bymeans of the coil 7, the solder melts and flows into the space 2 in theliquid condition. Because as a result of the arrangement of thehigh-frequency coil only the free end 8 of the contact pin is mainlyheated and the remaining part of the contact pin remains cold, theliquid solder which flows into the space between the current conductorand the narrowing will cool before the flow of liquid has reached thewidening 4. As shown in FIG. 2, the lower limit of the solidified solderis in the proximity of the edge 9 which marks the transition of thenarrowing to the widening. The space 2 is filled substantially entirelyby the solidified solder 9.

Instead of a body which is formed from a helically wound wire, acylindrical member of solder may also be used. Such a member is shown inFIG. 4.

As shown in FIG. 3, the lamp cap 10 during the manufacture of the lampis secured in a stand 11. The contact pins 12 and 13 project through thebottom portion 14 of the stand 11. The lamp envelope 15 of theincandescent lamp to be manufactured with the filament 16 arrangedtherein is supported by a holder (not shown) which is movable relativeto the stand. The movements of the holder are controlled by an adjustingdevice comprising optical auxiliary means. The free ends of the contactpins 12 and 13 are each surrounded by high-frequency coils l7 and 18,respectively. The

bottom portion 14 is further covered by a hood 19 below which a reducinggas is present during the soldering operation.

When the filament has been aligned relative to the lamp cap and thesoldering operation has been carried out, the incandescent lamp isremoved from the stand after which the space between the lamp cap 10 andthe lamp envelope 15 is filled with a cement to reinforce the mutualconnection.

It will be obvious that instead of a high-frequency coil, flames mayalso serve as heating members.

If desired, the free ends of the contact pins may be ground after thesoldering and cementing operation.

What is claimed is:

1. An electric incandescent lamp having an envelope which comprises alamp cap manufactured from an insulating material a pair of elongatedcontact pins each having an axial passageway therein, said pins beingcarried by said lamp cap, and a current conductor extending from thelamp envelope through each passageway, each of said conductors beingsoldered in said passageway in which said conductor is disposed, each ofsaid passageways comprising first, second and third axial sections, saidsecond axial section having a crosssectional area smaller than saidfirst and third sections, said third section being disposed distal tothe lamp envelope and being the axial extremity of said pin, said thirdaxial section being at least partly filled with solder each of saidaxial sections being dimensional in closely spaced engagement with thecircumference of said conductor carried therein, said closely spacedrelationship permitting the flow of molten solder therebetween andsubstantially limiting radial play therebetween.

2. An electric incandescent lamp as claimed in claim 1 wherein saidsolder extends axially in each of said contact pins into said secondaxial section.

3. An electric incandescent lamp as claimed in claim 2, wherein saidthird axial section forms a truncated cone in the axial portion thereofproximate said second axial section.

4. The apparatus as described in claim 1 wherein said first and thirdaxial sections taper smoothly into said second axial section.

1. An electric incandescent lamp having an envelope which comprises alamp cap manufactured from an insulating material a pair of elongatedcontact pins each having an axial passageway therein, said pins beingcarried by said lamp cap, and a current conductor extending from thelamp envelope through each passageway, each of said conductors beingsoldered in said passageway in which said conductor is disposed, each ofsaid passageways comprising first, second and third axial sections, saidsecond axial section having a cross-sectional area smaller than saidfirst and third sections, said third section being disposed distal tothe lamp envelope and being the axial extremity of said pin, said thirdaxial section being at least partly filled with solder each of saidaxial sections being dimensional in closely spaced engagement with thecircumFerence of said conductor carried therein, said closely spacedrelationship permitting the flow of molten solder therebetween andsubstantially limiting radial play therebetween.
 2. An electricincandescent lamp as claimed in claim 1 wherein said solder extendsaxially in each of said contact pins into said second axial section. 3.An electric incandescent lamp as claimed in claim 2, wherein said thirdaxial section forms a truncated cone in the axial portion thereofproximate said second axial section.
 4. The apparatus as described inclaim 1 wherein said first and third axial sections taper smoothly intosaid second axial section.